#include<iostream>
using namespace std;
typedef long long LL;

const int N = 1e7 + 10;
LL f[N];
LL v[N], w[N];
LL n, m;
int main()
{
	cin >> m >> n;
	for (int i = 1;i <= n;i++)
	{
		cin >> v[i] >> w[i];
	}
	for (int i = 1;i <= n;i++)
	{
		for (int j = v[i];j <= m;j++)
		{
			f[j] = max(f[j], f[j - v[i]] + w[i]);
		}
	}
	cout << f[m] << endl;
	return 0;
}